This is not how the 2015 season was supposed to go for the Red Sox. Having rebuilt their rotation almost from scratch and having spent a combined $255.5 million on free-agent hitters Hanley Ramirez, Pablo Sandoval and Cuban outfielder Rusney Castillo, the Red Sox were supposed to be among the most improved teams in baseball this year after finishing fifth in the American League East last season. Instead, as we enter the second week of May, Boston is again in last, thanks in large part to the dismal performance of that rebuilt rotation. With Ramirez having suffered a shoulder injury Monday night in Boston's fourth consecutive loss, there’s precious little reason for optimism in Fenway.

Shifted from shortstop to leftfield upon signing with Boston—in part in the hope that he could stay healthy playing a less demanding position—Ramirez has been the Red Sox’ best hitter thus far this season, hitting .283/.340/.609 and leading the team in slugging, home runs (10), RBIs (22), runs scored (17), total bases (56), OPS (.949) and OPS+ (158). His transition on defense hasn't gone nearly as well, however. In top of the first inning against the Rays on Monday night, Ramirez proved he could get hurt just as easily in the outfield, slamming his left shoulder into the side wall in leftfield after making a running catch (which was ruled a two-base error after the wall caused him to drop the ball).

Ramirez’s injury has been termed a shoulder sprain, and the Red Sox have said it’s not clear that he will have to go on the disabled list. But he will still miss some time, and it’s quite possible that the injury could impact his performance at the plate. It’s worth noting here that Ramirez has had surgery on that shoulder twice in his career: In October 2007, he had a torn labrum in the joint repaired, and in September 2011, he had it fixed again after suffering a separation in the joint. Watching Monday’s game, it looked like Ramirez had separated his shoulder again, and while it’s encouraging that he didn’t, there’s still ample cause for concern regarding his condition.

A healthy Ramirez is vital to Boston's hopes, as the Red Sox need all the runs they can get thanks to their disaster of a pitching staff. Only the mile-high Rockies have allowed more than Boston’s 5.35 runs per game this season, and no team in baseball has worse rotation ERA than the Red Sox’ 5.73 mark.

After trading Jon Lester, John Lackey and Jake Peavy at last year’s non-waiver deadline and failing to convince Lester to return to Boston as a free agent, the Red Sox set to work building a rotation of less celebrated ground-ball pitchers whom they hoped would thrive in front of Boston’s strong infield defense, upgraded by the addition of Sandoval at third base. Thus far, however, none of Rick Porcello, Justin Masterson, Wade Miley, and Joe Kelly are getting ground balls at their established rates. Of that group, only Masterson, the most extreme ground-baller of the bunch over the course of his career, has induced more ground balls than fly balls this season. Both he and Porcello, who was acquired from the Tigers prior to his walk year and has since been signed to a four-year, $82.5 million extension, have thus far posted the lowest groundball-to-flyball percentages of their careers. On top of that, Porcello has allowed the fourth-most home runs allowed in the AL with six in just five starts. The rotation as a whole, meanwhile, ranks 16th in the majors in groundball-to-flyball ratio.

That would be troubling enough if Miley didn’t have the worst strikeout (5.2 per nine) and walk (4.4) ratios of his career, or if Porcello’s walk rate (2.8/9) hadn’t inflated with his home run rate. Outside of his ground-ball rate, Masterson has largely pitched in line with his career numbers, but that’s not a good thing, given that Masterson has a career ERA+ of 94, below league average, and a career strikeout-to-walk ratio barely over 2.00. Among those four, none has a better fielding independent pitching figure than Joe Kelly’s 3.73, and Kelly is a pitcher who has never thrown more than 124 innings in a major league season.

Then there’s Clay Buchholz, who is leading the AL with 11.5 strikeouts per nine innings but is 1–4 with a 6.03 ERA despite that figure. Buchholz, whose groundball-to-flyball ratio this season is actually better than both Porcello's and Kelly’s thus far, is the one Boston starter to have pitched in poor luck, with opponents hitting .407 on balls in play against him. That figure is sure to come down, but that doesn’t mean Buchholz isn’t getting hit hard. Per Baseball-Reference.com, 30% of the balls put in play against him have been line drives, putting him in the top quarter of qualified starting pitchers in that category.

Given all of that, the last thing the Red Sox need is to lose their most productive bat for an extended period. Indeed, the thought of removing Ramirez from Boston's lineup helps illustrate the degree to which he has been propping it up. Mike Napoli, Xander Bogaerts and wünderkindMookie Betts are each currently sporting an OPS below .700. Injuries have forced top catching prospect Blake Swihart to the majors ahead of schedule and charged him with improving another sagging spot in the lineup. Rightfield has thus far been a black hole (.144/.250/.222): Shane Victorino is back on the disabled list with a hamstring strain, Allen Craig and Daniel Nava are both off to poor starts, and Brock Holt’s bat has gone cold. Castillo, meanwhile, was sent down to Triple A in spring training and lost most of the month of April to a shoulder injury.

Boston desperately needs its four star hitters—Ramirez, David Ortiz, Dustin Pedroia and Sandoval, the last of whom is off to a strong if underpowered start to his Red Sox career—to carry the team right now, if that’s even possible. Even with Ramirez’s hot start, the Red Sox are the only team in the AL East with a negative run differential. If they lose Ramirez or his established level of production for an extended period, their season may already be sunk.